Angle-measuring devices for sensing the angular position of a shaft are widespread in automation technology and in machine tools. They are used, for example, to determine, in closed-loop drive mechanisms, actual position values which are needed by subsequent electronics, such as a numerical control system, to calculate setpoints for control circuits used to control the drive mechanism (e.g., the feed rate of a tool or workpiece). To this end, a mechanically rigid connection is made between the encoder shaft and the machine shaft, so that movement of the machine shaft is transmitted directly to the encoder shaft. For the purpose of determining the rotation angle of the shaft to be measured, angle-measuring devices include a material measure, which is usually in the form of a code disk having a graduation structure applied thereto. By scanning the graduation structure, it is possible to determine the angular position of the shaft. This is done using, for example, optical, magnetic or inductive scanning principles. The angle measurement may be based on incremental and/or absolute measurement principles.
Today, it is preferred to use angle-measuring devices which, regardless of whether the underlying measurement principle is absolute or incremental, or both absolute and incremental, generate absolute angle values which are transmitted from the position-measuring device to subsequent electronics via digital, usually serial, data interfaces.
Especially in cases where an angle-measuring device is intended to measure the angular position of a shaft of a drive mechanism that moves heavy loads, such as, for example, the drive of a rotary table axis in a machine tool, or when high rotational speeds are required, such as in the case of a machine tool spindle, it is important that the mass moved by the drive not have an imbalance with respect to the axis of rotation of the shaft.
WO 2009/156094 describes an electromechanical balancing system. For purposes of determining the imbalance, separate sensors are needed to detect the rotational speed and the vibrations caused by the imbalance. The analysis of the sensor signals is performed in a distributed manner.